Spinal cord injury (SCI), a major health-care problem, warrants pathophysiological and therapeutic study to minimize damage for functional recovery. Increased calpain activity and expression concomitant with structural protein loss in SCI lesions indicate a pivotal role for this protease in the irreversible cell damage. Partially damaged cells in the area surrounding a necrotic lesion (traumatic penumbral) and areas adjacent to the traumatic penumbra may be rescued or protected by calpain inhibitors, facilitated by additional drugs, synergistic for tissue protection. Since many pathways participate in secondary tissue destruction in SCI, calpain inhibitor inclusion with other agents that block degradative reactions could offer more potent neuroprotection. Their specific aims are to: (1) Define calpain's expression in both the SCI necrotic lesion and the surrounding traumatic penumbra and its adjacent areas which have a potentially reversible apoptotic component; (2) Examine strategies to improve neuroprotection in SCI that emphasize exploration and delineation of synergistic agents affecting reactions in the secondary injury cascade; (3) Study calpain's role in the induction of apoptosis in vitro and how this is related to events and their constraint by specific calpain inhibitors in the traumatic penumbra. To support these aims, they will: (1) Determine activity and expression (mRNA and protein levels) of u and mcalpain and their inhibitor, calpastatin; ascertain their cellular localization by double-label immunofluorescence; define the extent and nature of cell death in defined areas of the cord following injury; (2) Study the therapeutic effects and synergy of calpain-specific cell permeable inhibitors (calpeptin, E64-d, MDL-28170) with methylprednisolone, indomethacin and brain-derived neutrotrophic factors in acute and chronic SCI, examining parameters indicated previously; correlate changes with behavioral outcome; (3) Determine the effect of cytokines on calpain activation in neural cell culture, examining apoptotic characteristics (biochemical and morphological) effected by calpain inhibitors.